Unusual skeletal morphology and systematic description of a new Devonian cryptostome bryozoan from the Western Sahara

Abstract

Palaeozoic bryozoan colonies display a large variety of skeletal elements. Various types of rod-like styles are mainly built by laminated and non-laminated (hyaline) skeleton. Typical styles consist of hyaline cores and surrounding laminated sheaths. They usually protrude on the colony surface as spines. In a new bryozoan genus from the Middle Devonian of the Western Sahara described here, styles do not protrude on the colony surface and are embedded within the laminated skeleton. They consist of fibrous material. This new type of styles, unknown from other bryozoans, is here called a “cryptostyle”. A special characteristic of these structures is their intensive reddish-brown colouration. This colouration is apparently caused by the presence of ferric iron between the individual fibres. The function of cryptostyles was apparently weight reduction and stabilising the skeleton. The general morphology of the new bryozoan, Cryptostyloecia hexapuncta gen. et n. sp., implies its systematic position within ptilodictyine cryptostomes, specifically the Family Ptilodictyidae Zittel, 1880.